alt131 - 5:36 pm on Sep 19, 2012 (gmt 0)
Nice reference, MinosTheNinth, and something I haven't investigated much either, so I'd be interested in comments from anyone who has. As the article refers, there is also 6.1. ‘box-sizing’ property [w3.org] which was initially thought to be the solution for this, but is now at risk element and may not go forward.
There are also 18.4 Dynamic outlines: the 'outline' property [w3.org], which is drawn outside the box (so may require a margin to make sure the box does not overlap other elements).